The present invention generally relates to a system and method for monitoring a fluid in a fluid-containing system. More specifically, the present invention relates to a monitoring device and method for monitoring surface fouling in fluid-containing systems.
It is, of course, generally known to provide a fluid system in which fluid is transported from one location to another location. One such example is a water cooling tower in which heat exchange tubing is provided for transport of water from a first location to a second location. In such a system, unwanted film or fouling is often created on internal surfaces of the tubing. The film is typically due to microorganisms or colored or particulate matter suspended in the water flowing in the system. The film typically grows in thickness reducing the efficiency of, for example, heat transfer from a hot interior to a cooler ambient environment.
Of course, many other systems that implement fluid transfer are known. For example, although the fluid may be water, it could be natural gas in a transmission line. The film may be caused by any material in the fluid strain whether biological or even inorganic trapped in the fluid.
One film fouling monitoring device is taught and described in U.S. Pat. No. 5,185,533 to Banks et al. In the '533 patent, a system is provided for determining accumulative film thickness at the inside diameter of a main stream conduit conducting a main stream of a flowing fluid by using a transparent shunt conduit to shunt from the main stream a sample stream of the process fluid. A reference light emitter and light detector at a referenced section of the shunt is provided wherein any appreciable film is removed. An upstream sample light emitter and detector are opposed thereto wherein any film is allowed to form. A common source of light is provided so that respective emitters emit light beams of the same intensity. Means for determining concurrently intensities of light received by the detectors whereby film thickness may be determined for the sample is also provided.
Accordingly, Banks et al. teach a device which uses two light paths from a single light source. Both light paths go through a transparent tube although one of the beams goes through a section of the tube kept free of deposits by a mechanical wiper. This clean section reading allows the reading from the fouled section of the tubing to be corrected for any effects of color or turbidity in the water. This device, however, is rather expensive given the cost of the mechanical wiper assembly. In addition, such a wiper assembly, being mechanical in nature, can be unreliable.
A need, therefore, exists for a less complex and less costly system and method for monitoring for fouling in a fluid stream that is both reliable and inexpensive. As a result, control and optimized feeding of antifouling and biocidal treatments may be added to the system following monitoring.